One advantage of common mode logic (CML) transmitters is that they operate at high speeds. One disadvantage, however, is that CML transmitters continuously burn current. In some CML transmitter applications power saving measures are employed to reduce the power consumption that is required to continuously provide current. In such instances the main power source of the CML transmitter is switched off and an auxiliary power source is switched on when the CML transmitter is placed into a power conservation state.
PCIExpress is a well known serial bus interface standard. One of the PCIExpress power conservation states is referred to as a P2 state. Assume that a CML transmitter has been placed in a PCIExpress P2 state and is operating on an auxiliary power source. Some level of functionality in the CML transmitter must still be maintained in order for the CML transmitter to operate properly. For example, the CML transmitter must operate in a P2 Beacon mode in order to indicate the existence of a valid serial connection. In a P2 Beacon mode the CML transmitter needs to switch to a separate regulated power supply.
There is a need in the art for an improved system and method for providing power managed CML transmitters for use with main and auxiliary power sources. There is also a need in the art for an improved system and method for switching between a main power source for a CML transmitter and an auxiliary power source for the CML transmitter.